From: Dust Li dust.li@linux.alibaba.com
[ Upstream commit 6bf536eb5c8ca011d1ff57b5c5f7c57ceac06a37 ]
rmbe_update_limit is used to limit announcing receive window updating too frequently. RFC7609 request a minimal increase in the window size of 10% of the receive buffer space. But current implementation used:
min_t(int, rmbe_size / 10, SOCK_MIN_SNDBUF / 2)
and SOCK_MIN_SNDBUF / 2 == 2304 Bytes, which is almost always less then 10% of the receive buffer space.
This causes the receiver always sending CDC message to update its consumer cursor when it consumes more then 2K of data. And as a result, we may encounter something like "TCP silly window syndrome" when sending 2.5~8K message.
This patch fixes this using max(rmbe_size / 10, SOCK_MIN_SNDBUF / 2).
With this patch and SMC autocorking enabled, qperf 2K/4K/8K tcp_bw test shows 45%/75%/40% increase in throughput respectively.
Signed-off-by: Dust Li dust.li@linux.alibaba.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/smc/smc_core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c index d1cdc891c211..f1dc5b914771 100644 --- a/net/smc/smc_core.c +++ b/net/smc/smc_core.c @@ -1904,7 +1904,7 @@ static struct smc_buf_desc *smc_buf_get_slot(int compressed_bufsize, */ static inline int smc_rmb_wnd_update_limit(int rmbe_size) { - return min_t(int, rmbe_size / 10, SOCK_MIN_SNDBUF / 2); + return max_t(int, rmbe_size / 10, SOCK_MIN_SNDBUF / 2); }
/* map an rmb buf to a link */